Acknowledgments

This publication was written by Bennett W. Fletcher, Ph.D.,
Redonna K. Chandler, Ph.D., and the Office of Science Policy and
Communications, National Institute on Drug Abuse.

This publication is in the public domain and may be used or
reproduced in its entirety without permission from NIDA or the
authors. Citation of the source is appreciated.

The U.S. Government does not endorse or favor any specific
commercial product or company. Trade, proprietary, or company
names appearing in this publication are used only because they are
considered essential in the context of the studies described here.